Water immiscible rosin mildly activated flux

ABSTRACT

Embodiments of the present invention are directed to modified rosin mildly activated (RMA) fluxes and methods of soldering components on printed circuit boards. The modified RMA flux includes a RMA flux material and a randomizing additive. The randomizing additive causes misalignment of the hydrogen bonds between terpine polymer chains created from the RMA flux material during soldering. The resulting modified RMA flux performs as well as, or better than traditional RMA fluxes, but the flux residue remaining after soldering can be removed with a highly polar solvent, such as soapy water.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.12/381,276, filed Mar. 9, 2009, entitled WATER IMMISCIBLE ROSIN MILDLYACTIVATED FLUX the entire contents of which are incorporated herein byreference.

FIELD OF THE INVENTION

The invention is directed to water immiscible rosin mildly activated(RMA) fluxes, and to methods cleaning the fluxes from electroniccomponents. More particularly, the invention is directed to modified RMAfluxes that can be cleaned from electronic components using a highlypolar solvent.

BACKGROUND OF THE INVENTION

Printed circuit boards are used in a wide variety of electronic devices,including computers and communications equipment, among otherapplications. The printed circuit boards are assembled by solderingcomponents to conductive contacts on the board. The soldering may beaccomplished by a number of different techniques, but serves to attachand electrically connect the components and conductive contacts to theboard. Prior to soldering, however, a flux is usually applied to thesurfaces intended to be joined. The flux chemically prepares thesurfaces to receive the solder by removing and preventing the formationof stannous and stannic oxides on the surfaces. This promotes wettingand continuity of the solder at the interface with the circuit, therebyimproving the quality and integrity of the electrical and mechanicalconnections between the adjoining surfaces.

After soldering the fluxed surfaces, and the assembly is cooled, thesolder hardens and residual flux polymerizes to form deposits on theexposed surfaces. If allowed to remain on the printed circuit board, theresidual flux can cause circuit failure due to stress corrosionresulting from exposure to temperature and humidity. In extreme cases,the flux residue can cause joint fatigue/cracking as there exists acoefficient of thermal expansion (CTE) mismatch between the flux polymerand the metal of the solder joint. Accordingly, the residual flux mustbe cleaned from the board.

Fluxes useful in electronics applications include rosin fluxes and watersoluble fluxes. While rosin fluxes have been more traditionallyemployed, water soluble fluxes have gained interest due to their lowervolatility and compliance with environmental requirements that arebecoming ever more stringent. However, water soluble fluxes are muchmore corrosive than rosin fluxes, making them a less desirable flux forelectronics applications. In particular, although water soluble fluxesmay be removed with water, if they are not properly cleaned, theresidual flux will degrade the treated electronic device. Specifically,the residual flux is chemically active, hydroscopic in nature, and willcause corrosion and etching of the metals, including the very electroniccomponents that it was employed to help solder. The residual flux fromwater soluble fluxes puts long-term hardware performance at risk,negatively affects the performance of diode junctions, and makes costlyfield failures likely. Accordingly, rosin fluxes continue to be widelyused in electronics applications.

One traditional category of rosin fluxes is rosin mildly activated (RMA)fluxes, which are water resistant. Because RMA fluxes are waterresistant, their removal requires the use of organic solvents such asfreon, trichloroethane, trichloroethylene, toluene, and isopropylalcohol. However, in light of environmental restrictions which arebecoming more stringent, removing RMA fluxes has become a daunting task.While discovering low volatile organic compound (VOC) cleaning chemicalshas proved difficult, one proposed method of cleaning such fluxesincludes “bomb proof” closed-loop systems for containing the VOCsresulting from the use of organic solvents. Although these “bomb proof”systems enable compliance with environmental regulations, they are verycostly, requiring substantial investments in facility upgrades and newequipment.

In addition, RMA fluxes are stored in an isopropyl alcohol carrier.Because the isopropyl alcohol carrier evaporates rapidly when exposed toair, the pot life of traditional RMA fluxes has historically beenlimited.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, a modified rosin mildlyactivated (RMA) flux includes a RMA flux material and a randomizingadditive. The RMA flux material may be any such material known in theart, including but not limited to RMA flux materials available fromAlphaMetals, Inc. (Jersey City, N.J.). The randomizing additive may beany additive that cause misalignment of the hydrogen bonds betweenterpine polymer chains created from the RMA flux material duringsoldering. Nonlimiting examples of suitable randomizing additive includehydrocarbon oils, naturally occurring oils, glycols, and mixturesthereof. The randomizing additive may be present in the modified RMAflux in a concentration ranging from about 3% to about 45%. Theresulting modified RMA flux performs as well as, or better thantraditional RMA fluxes, but the flux residue remaining after solderingcan be removed with a highly polar solvent, such as soapy water.

According to another embodiment of the present invention, a method ofsoldering components on a printed circuit board includes mixing a RMAflux material with a randomizing additive to form a modified RMA flux,applying the modified RMA flux to the printed circuit board, solderingat least two components of the circuit board, and removing the modifiedRMA flux using a polar solvent. The polar solvent may be any saponifyingmedia, such as soapy water. For example, the polar solvent may includean aqueous amine solution in deionized water. The method may furtherinclude repeating flux application and removal. In addition, the methodmay further include cleaning the circuit board in a polar solvent heatedto about 70 to about 80° C. In addition, the method may further includerinsing the circuit board in deionized water heated to about 80 to about90° C., and drying the circuit board at a temperature ranging of about80° C.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of the patent or patent application publication with colordrawings will be provided by the Office upon request and payment of thenecessary fee.

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings, wherein:

FIG. 1 is a picture of a modified RMA flux according to one embodimentof the present invention, where the modified RMA flux was exposed to airfor two hours;

FIG. 2 is a picture of a RMA flux according to the prior art, where thetraditional RMA flux was exposed to air for two hours;

FIG. 3 is a picture showing a component being soldered onto thesubstrate of a circuit board using a modified RMA flux according to oneembodiment of the present invention;

FIG. 4 is a picture showing a component being soldered onto thesubstrate of a circuit board using a RMA flux according to the priorart;

FIG. 5 is a picture of a cleaned circuit board which had been solderedusing a modified RMA flux according to one embodiment of the presentinvention;

FIG. 6 is a picture of a cleaned circuit board which had been solderedusing a traditional RMA flux;

FIG. 7 is a picture of a modified RMA flux according to one embodimentof the present invention applied on glass slides;

FIG. 8 is a picture of a RMA flux according to the prior art applied onglass slides;

FIG. 9 is a picture of the glass slides of FIG. 7 after cleaning;

FIG. 10 is a picture of the glass slides of FIG. 8 after cleaning.

DETAILED DESCRIPTION OF THE INVENTION

In some embodiments of the present invention, a modified rosin mildlyactivated (RMA) flux is water immiscible and effectively removed with apolar solvent, such as soapy water. The modified RMA flux according toembodiments of the present invention has the properties of traditionalRMA fluxes, such as inactivity until heated to soldering temperatures,good cleaning action (once good metal joints are formed duringsoldering), and inert residue if the geometries of the electronic partdo not allow for ease of cleaning. However, in contrast to traditionalRMA fluxes, which require organic solvents having high levels ofvolatile organic compounds (VOCs) to remove the flux residue, theresidue from the modified RMA fluxes according to embodiments of thepresent invention can be cleaned with a polar solvent, such as soapywater. In addition to enabling use of flux residue cleaning mechanismsthat comply with stringent environmental regulations, the modified RMAfluxes according to embodiments of the present invention result inreductions in the cost of materials and increased efficiency as comparedto current organic solvent cleaning chemicals, which require largeramounts of solvent and drastic measures to comply with strictenvironmental standards. Comparatively, a soapy water solution from aconcentration of about 7 to about 14% has shown substantially completeremoval of this water-immiscible RMA flux.

In one exemplary embodiment, the modified RMA flux includes a RMA fluxmaterial and a randomizing additive. The RMA flux material may be anysuitable RMA flux material known in the art. Nonlimiting examples ofsuitable flux materials include Alpha Metals Superior 611 (RMA) fromAlphaMetals, Inc. (Jersey City, N.J.), Flux 185 (RMA) from Kester Inc.,Flux 197 (RMA) from Kester Inc., #5RMA soldering flux (IndiumCorporation, Clinton, N.Y.), KR-19 RMA soldering flux (Nihon-Almit,Tokyo, Japan), and RMA flux 202-25 from AIM. In one embodiment, forexample, the RMA flux material may be any such flux material obtainedfrom AlphaMetals, Inc., including but not limited to Alpha® 611.

The randomizing additive serves to modify the RMA flux material into awater immiscible product. As used herein, “water immiscible” means thatthe flux residue is from about 1 to about 5% absorptive, and can beremoved by a polar solvent or soaping agent, for example soapy water orany other saponifying media. An understanding of the mechanism by whichthe modification takes place can be furthered by understanding why theRMA flux material (without the additive) is water resistant. Duringsoldering, the RMA flux material is converted into long chainterpine-based polymers, as shown in Formula 1, below.

Separate terpine-based polymer chains are attracted to and bonded toeach other through hydrogen bonds that form between oxygen atoms of onechain and hydrogen atoms to another chain. The resulting structure isrepresented by Formula 2, below, in which the hydrogen bonds aredepicted by dashed lines between the oxygen and hydrogen atoms.

As shown in Formula 2, the linked polymer chains form a dense compounddue to the inter-chain hydrogen bonding of the long polymer chains. Whenmultiple layers of polymer chains are stacked, the compact/linear natureof the linked chains effectively renders the cured RMA matrix waterresistant because water molecules are incapable of penetrating thedensely linked structure. Accordingly, the traditional method ofremoving the flux residue has been the use of organic solvents, whichcan penetrate the stacked polymer layers to break the long terpinepolymer chains into shorter segments and solvate the hydrogen bonds.However, the best method to solvate these polymer chains requires theuse of solvents having high VOC levels. As environmental standardsbecome stricter, the traditional method of removing flux residue becomesincreasingly onerous. In particular, special equipment must be used torecapture the VOCs, and increased labor costs result from new proceduresand record keeping requirements to remain EPA and AQMD compliant.

In embodiments of the present invention, however, the randomizingadditive is believed to interrupt the polymerization process duringsoldering, thereby creating shorter polymer chains and discontinuoushydrogen bonds in longer polymer chains. Though the change in polymerchain length is not great enough to affect the performance of thematerial as a soldering flux, used in this case as an oxygen barrier,the shorter chain length results in misalignments in the polymerstructure during inter-chain hydrogen bonding. These misalignmentscreate gaps along the paired chain matrix, as shown in Formula 3, below.

The gaps created in the linked polymer chain allow molecules of polarsolvents (such as water molecules in soapy water) to interrupt thehydrogen bonds and solvate the cured modified RMA flux residue withinthe gaps of the long misaligned chain, similar to thenon-polar/hydrocarbon solvents used to solvate hydrogen bonds aspreviously discussed. The resulting soapy organic slurry can be removedby mechanical blotting with a cloth or by a water rinse.

The modified RMA fluxes according to embodiments of the presentinvention not only meet long-term hardware durability requirements, butalso result in environmentally acceptable waste products. In addition,depending on the saponifying agent used, the waste slurry may bebiodegradable.

In addition, the modified RMA fluxes according to embodiments of thepresent invention can be more effectively cleaned from the substratecompared to traditional RMA fluxes. Highly polar solvents, such as soapywater, can dissolve the flux residue even under components where fluxresidues can usually hide.

The randomizing additive may be any material capable of causingmisalignments in the linked polymer chain. Nonlimiting examples ofsuitable randomizing additives include hydrocarbon oils, naturallyoccurring oils, glycols, and combinations thereof. Specifically, somenonlimiting examples of suitable hydrocarbon oils include castor beanoil, corn oil, grape seed oil, olive oil, peanut oil, soybean oil,sunflower seed oil, walnut oil, avocado oil, flax seed oil andcombinations thereof. Also, some nonlimiting examples of suitablenaturally occurring oils include glycerin, jojoba, hemp oil, lanolin,tea tree oil, wheat germ oil, and combinations thereof. In addition,some nonlimiting examples of suitable glycols include benzo-alkyl diols,polyethylene glycols, ethylene adipates, and combinations thereof. Inone exemplary embodiment, the randomizing additive is grape seed oil.

In some embodiments, a single randomizing additive may be used in themodified RMA flux. In other embodiments, however, combinations of atleast two additives may be used. For example, a combination of two ormore additives from the same group may be used, such as two or morehydrocarbon oils. Alternatively, two or more additives from differentgroups may be used, such as one hydrocarbon oil and one naturallyoccurring oil, or one oil and one glycerol. When the combination ofadditives includes two materials from the same group (e.g., twohydrocarbon oils), any mixing ratio may be used. When the combination ofadditives includes at least two materials from different groups, anymixing ratio may also be used. However, in one embodiment, when thecombination includes a mixture of oils (either hydrocarbon or naturallyoccurring) and glycerols, the weight ratio of oil to glycerol rangesfrom about 5 to about 20% glycerol in oil. Longer chain oils (i.e.,those having higher molecular weight) are less effective at randomizingthe terpine polymer, while branched chain hydrocarbons are lesseffective than linear hydrocarbons. Ratios of glycerol to oil greaterthan about 20% glycerol in oil negatively affect the performance of therandomizing flux compared to using the hydrocarbon oil by itself.

The randomizing additive is present in the modified RMA flux in aconcentration ranging from about 3 wt % to about 45 wt %. In oneembodiment, when a smaller chain oil is used, the randomizing additivemay be present in an amount ranging from about 7 to about 15 wt %.However, longer chain oils (such as castor oil) require higherconcentrations of the oil in the flux media to produce the randomizingeffect. When the concentration of the additive is less than about 3 wt%, the chain length of the resulting terpine-based polymers is notshortened enough to cause sufficient misalignment in the linked polymerchain, and the polar solvent is therefore not sufficiently capable ofpenetrating the linked chain. Also, at concentrations greater than about45 wt %, the randomizing additive prevents formation of a solid polymer.When this occurs, the liquid may slough off the forming solder joint,allowing tin oxides to form. In particular, as higher concentrations ofrandomizing additives are used with a basic RMA flux, the concentrationof the flux activating agents decrease. For example, at 50 percentdilution, the resident RMA flux activator would be at half itsconcentration. Accordingly, the modified flux works best at higherdilutions. However, at some higher dilutions, flux activators, such asadipic acid or caproic acid, would need be added to compensate for theloss occurring as a result of the dilution. Additionally, the higherconcentrations of randomizing agents result in minimization of thepolymer effect, causing the flux to “thin out” at reflow. Therefore,according to embodiments of the present invention, the randomizingadditive is present in the modified RMA flux in a concentration rangingfrom about 3 to about 45 wt %.

Although the compatibility of the randomizing additive with the RMA fluxmaterial may vary depending on the selected additive and RMA fluxmaterial, and the compatibility of the additive and flux material mayaffect long-term effectiveness. However, any combination or permutationof randomizing additives included in an amount within the specifiedrange effectively renders the heat-treated modified RMA flux waterimmiscible and removable with a polar solvent or soaping agent.

According to another embodiment of the present invention, a method ofsoldering components on a printed circuit board includes mixing a RMAflux material with a randomizing additive to form a modified RMA flux,applying the modified RMA flux to at least one component of the printedcircuit board, soldering at least two components of the circuit board,and removing the modified RMA flux using a polar solvent. The polarsolvent may be any polar solvent or a saponifying media, such as soapywater. Other nonlimiting examples of suitable polar solvents includeAlphaMetals Armaclean 2000, Reactive Aqueous Defluxing Systems(RADS—sodium bicarbonate and hydrogen peroxide in water), Zestron AtronAC 200 and Atron 300. In one exemplary embodiment, the polar solvent mayinclude an aqueous amine solution in deionized water. One nonlimitingexample of a suitable aqueous amine solution is Aquanox® 4615US(available from Kyzen Corporation, Nashville, Tenn.). The aqueous aminesolution may be present in an amount of about 3 wt % or greater. Forexample, the aqueous amine solution may be present in an amount rangingfrom about 7 to about 30 wt %. In one embodiment, for example, theaqueous amine solution is present in a concentration of about 12 wt %.

The method may further include repeating flux application and removal,which may be repeated as many times as desired. In addition, the methodmay further include cleaning the circuit board in a polar solvent heatedto about 70 to about 80° C. In one embodiment, for example, the polarsolvent is a 12 wt % aqueous amine solution (such as Aquanox® 4615US) indeionized water. The method may further include rinsing the circuitboard in deionized water heated to about 80 to about 90° C., and dryingthe circuit board at a temperature of about 80° C.

In one exemplary embodiment, a method of soldering components on aprinted circuit board includes preparing a modified RMA flux by mixing10 wt % of a randomizing additive (e.g., grape seed oil) in 90 wt % of aRMA flux material. The modified RMA flux is applied on the substrate ofa printed circuit board, and the desired components are soldered to thesubstrate. The modified RMA flux is then removed using a soapingsolution or polar solvent, such as a 12 wt % aqueous amine solution(such as Aquanox® 4615US) in deionized water. The application andremoval of the modified RMA flux may be repeated as many times asdesired. The printed circuit board is then cleaned in a polar solvent orsoaping solution (such as a 12 wt % aqueous amine solution in deionizedwater) heated to a temperature ranging from about 70 to about 80° C. Theprinted circuit board is then rinsed in deionized water heated to atemperature ranging from about 80 to about 90° C., and the printedcircuit board is then dried at a temperature of about 80° C.

The following Examples are presented for illustrative purposes only, anddo not limit the scope of the present invention.

Example 1 Depicted in FIG. 1

A modified RMA flux was prepared by mixing 1 gram of grape seed oil in 9grams of Alpha 611 (a standard RMA flux available from Alpha Metals,Inc.; Jersey City, N.J.). The modified RMA flux was applied on thesubstrate of a printed circuit board, and components were soldered tothe substrate. The modified RMA flux was then removed using a 12 wt %aqueous amine solution (Aquanox® 4615US available from Kyzen Corp.;Nashville, Tenn.) in deionized water.

Comparative Example 1 Depicted in FIG. 2

Alpha 611 was used to solder desired components to the substrate of thecircuit board, as in Example 1. The Alpha 611 was then removed using thesame method as in Example 1.

Equal amounts of the fluxes of prepared as in Example 1 and ComparativeExample 1 were placed in separate containers and exposed to air for twohours. FIG. 1 depicts the modified RMA flux of Example 1 after exposureto air, and shows that the modified RMA flux according to Example 1remains in the liquid state after exposure to air. FIG. 2 depicts thestandard RMA flux of Comparative Example 1, and shows that the standardRMA flux of Comparative Example 1 is completely dried after exposure toair. Accordingly, FIGS. 1 and 2 demonstrate that standard RMA fluxesquickly evaporate when exposed to air, while the modified RMA flux ofExample 1 has a significantly greater pot life.

FIG. 3 depicts a component being soldered to a circuit board using a themodified RMA flux of Example 1. FIG. 4 depicts a component beingsoldered to a circuit board using the standard RMA flux of ComparativeExample 1. As shown in FIGS. 3 and 4, the modified RMA flux of Example 1produces little, if any, soldering fumes compared to the traditional RMAflux of Comparative Example 1.

FIG. 5 depicts a circuit board that has been cleaned after solderingusing the modified RMA flux of Example 1. FIG. 6 depicts a circuit boardthat has been cleaned after soldering using the standard RMA flux ofComparative Example 1. FIG. 6 depicts a circuit board that has beencleaned after soldering using the standard RMA flux of ComparativeExample 1. After cleaning, the circuit boards were tested forcontamination using an Ionic Contamination Test System (available fromAqueous Technologies; Rancho Cucamonga, Calif.). As shown in FIG. 5, themodified RMA flux of Example 1 showed a total contamination of 1.1 μg.As shown in FIG. 6, the standard RMA flux of Comparative Example 1showed a total contamination of 224.6 μg.

Accordingly, as shown in FIGS. 5 and 6, the circuit board soldered usingthe modified RMA flux of Example 1 was over 100 times cleaner aftersoldering and cleaning than the circuit board soldered using thestandard RMA flux of Comparative Example 1. The flux residue is visuallydepicted in FIG. 6 as the white haze directly to the left of componentSO16 and in between components CO16 and SOL20. In addition, more fluxresidue is visually depicted as a triangle on the bottom right corner ofcomponent TSOP32.

The modified RMA flux of Example 1 was then applied to glass slides, asdepicted in FIG. 7. Similarly, the standard RMA flux of ComparativeExample 1 was applied to glass slides, as depicted in FIG. 8. The glassslides were then cleaned. FIG. 9 depicts the glass slides of FIG. 7after cleaning, and FIG. 10 depicts the glass slides of FIG. 8 aftercleaning. As shown in FIGS. 9 and 10, the slides depicted in FIG. 9 aresignificantly cleaner than those depicted in FIG. 10. In addition, thestand-off distances (i.e., the distance between the bottom of the slidesand the substrate to which they were mounted) vary from right to leftbetween about 0.002″ and 0.030.″ The modified RMA flux (as compared tothe standard RMA flux) allows soapy water cleaning methods to remove amajority of processed flux contained in the stand-off area regardless ofthe stand-off area height variation. This is depicted in FIGS. 7 and 9(modified RMA flux) as compared to FIGS. 8 and 10 (standard RMA flux).

Like traditional RMA fluxes, the modified RMA fluxes according toembodiments of the present invention are compatible with many differentsoldering media and can be incorporated into flux pastes and screenprinted. However, the modified RMA fluxes according to embodiments ofthe present invention contain fewer volatile species than traditionalRMA fluxes. Traditional RMA fluxes use isopropyl alcohol as a carrier,but this carrier evaporates quickly when exposed to air, therebylimiting the pot life of the flux. In contrast, the modified RMA fluxesaccording to embodiments of the present invention use non-volatileadditives, produce fewer soldering fumes during processing, exhibitsubstantially less out-gassing (fume production) upon exposure to heat,have longer pot lives once exposed to air (e.g., in some embodiments,the modified RMA fluxes have pot lives exceeding 2 hours), and arenearly 100 times cleaner after soldering and cleaning than traditionalRMA fluxes.

In addition, the modified RMA fluxes according to embodiments of thepresent invention effect dramatic reductions in cost and significantincreases in productivity and efficiency. Given the recent tightening ofenvironmental standards, bringing the traditional RMA flux process intoenvironmental compliance will require significant equipment and processchanges having a drastic economic impact as compared to the changesrequired to implement a process using the modified RMA fluxes accordingto embodiments of the present invention. Considering aspects such asfacility upgrades, material costs, and labor costs, implementing aprocess for the use of the modified RMA fluxes according to embodimentsof the present invention will be substantially less costly thanimplementation of a process to continue use of standard RMA fluxes.

The modified RMA fluxes according to embodiments of the presentinvention would require facility enhancements including procuring adeionized water supply, installing plumbing to carry the deionized waterfrom the source, and ensuring adequate drainage for the deionized waterand soap slurry. For a facility with a capacity of about 300units/month, the approximate cost of installing plumbing for thedeionized water is $10,000, and the approximate costs of the drain andrelated pipeline is $20,000. To bring a similar facility usingtraditional RMA fluxes into environmental compliance would require a fargreater capital investment. For instance, such a facility would requirea scrubber unit costing approximately $350,000, as well as installationand ducting changes costing approximately $150,000. As seen by thiscomparison, the costs associated with changing from traditional RMAfluxes to the modified RMA fluxes according to embodiments of thepresent invention represent only 6% of the costs associated withbringing traditional RMA flux facilities into environmental compliance.Accordingly, for a 330 unit/month facility, changing from traditionalRMA fluxes to the modified RMA fluxes according to embodiments of thepresent invention represents a capital investment savings of $440,000.

The modified RMA fluxes according to embodiments of the presentinvention also present far lower recurring material costs. Inparticular, a suitable liquid soap for use in the modified RMA fluxesaccording to embodiments of the present invention costs about$60/gallon, and deionized water costs about $0.25/gallon. A 10% soapsolution is generally sufficient for cleaning purposes, and would costabout $6.23/gallon (i.e., 10% liquid soap costs $6, and 90% deionizedwater costs $0.23). In a facility with a capacity of 300 units/month,about 18 gallons/week of the soap solution would be required, yielding aweekly material cost of $112.14. In contrast, due to the lowerefficiency of the cleaning solution, traditional RMA fluxes require atleast double the amount of cleaning solution (with respect to thecurrent amount of 13 gallons/week). The traditional RMA flux cleaningsolutions cost about $180/gallon, and assuming that twice as muchsolution is needed to clean the same number of units (i.e., 26gallons/week), the weekly material cost for traditional RMA fluxfacilities is $4680. As seen from this comparison, the weekly materialcost of modified RMA facilities represents only about 2.4% of thematerial cost of traditional RMA flux facilities. Accordingly, changingfrom traditional RMA fluxes to modified RMA fluxes according toembodiments of the present invention represents a weekly material costsavings of $4567.86, or a yearly cost savings of $228,393 based on a 50week year.

In addition, the modified RMA fluxes according to embodiments of thepresent invention enable significant reductions in recurring laborcosts. Facilities using traditional RMA fluxes require additional stepsin the manufacture of printed circuit boards. In particular, additionallabor is required for loading and unloading the units into the“bomb-proof” closed-loop system, as well as for the increaseddocumentation requirements associated with VOC use. The total labor timeper board using traditional RMA fluxes is about 25.5 minutes, whereasthe total labor time per board using modified RMA fluxes according toembodiments of the present invention is about 16.2 minutes. As seen fromthis comparison, the labor time associated with the use of modified RMAfluxes according to embodiments of the present invention represents only64% of the labor time associated with the use of traditional RMA fluxes.Assuming a fully burdened labor rate of $90/hour and a monthly output of300 boards-per-month, facilities using traditional RMA fluxes incur amonthly labor cost of $11,475, and a yearly labor cost of $137,700. Incontrast, facilities using modified RMA fluxes according to embodimentsof the present invention incur a monthly labor cost of $7,290, and ayearly labor cost of $87,480, representing a monthly savings of $4,185and a yearly savings of $50,220. Accordingly, the use of modified RMAfluxes according to embodiments of the present invention representsabout a 36% decrease in labor costs as compared to the use oftraditional RMA fluxes.

As seen from the above cost comparisons, changing from the use oftraditional RMA fluxes to modified RMA fluxes according to embodimentsof the present invention results in dramatic reductions in operation andproduction costs. In particular, accounting for savings in facilitiesupgrades, materials, and labor, changing from traditional RMA fluxes tothe modified RMA fluxes according to embodiments of the presentinvention in a 300 unit/month facility results in a total savings perfacility in the first year of about $718,613, and a total savings perfacility over five years of about $1,833,065.

While the present invention has been illustrated and described withreference to certain exemplary embodiments, those of ordinary skill inthe art will understand that various modifications and changes may bemade to the described embodiments without departing from the spirit andscope of the present invention, as defined in the following claims.

What is claimed is:
 1. A method of soldering components on a printedcircuit board, the method comprising: applying a modified rosin mildlyactivated flux on a substrate of the printed circuit board, wherein themodified rosin mildly activated flux comprises a rosin mildly activated(RMA) flux material and a randomizing additive, wherein the rosin mildlyactivated flux is capable of being cleaned using an aqueous solution,and the randomizing additive is selected from the group consisting ofcastor bean oil, corn oil, grape seed oil, olive oil, soybean oil,sunflower seed oil, walnut oil, avocado oil, flax seed oil, glycerin,jojoba, hemp oil, lanolin, tea tree oil, wheat germ oil, benzo-alkyldials, ethylene adipates, and combinations thereof; soldering at leastone component to the substrate of the printed circuit board; removingthe modified rosin mildly activated flux from the printed circuit boardusing an aqueous solution; and after removing the modified rosin mildlyactivated flux from the printed circuit board, rinsing the printedcircuit board in de-ionized water heated to a temperature ranging fromabout 80 to about 90° C., and drying the circuit board.
 2. A method ofsoldering components on a printed circuit board, the method comprising:applying a modified rosin mildly activated flux on a substrate of theprinted circuit board, wherein the modified rosin mildly activated fluxcomprises a rosin mildly activated (RMA) flux material and a randomizingadditive, wherein the rosin mildly activated flux is capable of beingcleaned using an aqueous solution, and the randomizing additive isselected from the group consisting of castor bean oil, corn oil, grapeseed oil, olive oil, soybean oil, sunflower seed oil, walnut oil,avocado oil, flax seed oil, glycerin, jojoba, hemp oil, lanolin, teatree oil, wheat germ oil, benzo-alkyl diols, ethylene adipates, andcombinations thereof; soldering at least one component to the substrateof the printed circuit board; and removing the modified rosin mildlyactivated flux from the printed circuit board using an aqueous aminesolution.
 3. The method according to claim 2, wherein the aqueous aminesolution has a concentration of about 3 weight % or greater.